Each part has a significance.
The red cross with the Fleur-de-lis is from the coat of arms of Lincoln, the county town.
The green rectangles represent the agricultural nature of the county.
The blue rectangles represent the sea and the long coastline of Lincolnshire.
Finally the yellow lines refer to Lincolnshire's golden crops and to the fact that Lincolnshire born folk have been known traditionally as 'Yellerbellies'.
When the original idea of having a county flag was discussed it was decided to have a competition so residents could put forward their designs.
The full story about the flag can be read HERE.
Lincolnshire day is 1st October.
BTW. The animation is not my work but came from HERE.
